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I am struggling to understand the advantages over the Lewis Carroll method, which I find very simple and quick. It seems to add quite a lot of complexity.

by reedf1 2y ago

jgrahamc 2y ago
Really? Colin's method seems pretty simple to memorize and work with. Especially since it's all addition mod 7. Given that the mod operator distributes over addition you can work answers out easily while working with small numbers. For example, what day of week was September 2, 1945? 45/4 = 11 (mod 7 = 4) 45 mod 7 = 3 (easy to work out from 7 times table) September = 6 2 So you've got 4 + 3 (disappears under mod 7) and 6 + 2 mod 7 = 1. So, the second world war ended on a Sunday.
ColinWright 2y ago
I'm struggling to see why you think this is more complex ... the methods seem completely equivalent to me. The Carroll method does: 1: A calculation for the Century-Item ... divide by 4, take overplus from 3, multiply remainder by 2. 2: A calculation for the Year-Item ... Add together the number of dozens, the overplus, and the number of 4’s in the overplus. 3: A calculation for the Month-Item ... alternatively, memorise a table: the required final numbers after division by 7 are January, 0; February, 3; March, 3; April, 6; May, 1; June, 4; July, 6; August 2; September, 5; October, 0; November, 3; and December, 5. Note that these numbers are exactly those in my table, minus 1. 4: Include the Day-Item. Then add them all (mod 7) and convert the number to a month. It's exactly equivalent to what I described, except the Carroll method has additional calculations for the year.
- reedf1 2y ago
  Possibly it was in the clarity of his explanation. That makes sense, thank you.
ColinWright 2y ago
I think it's unreasonable for you to have been downvoted, and I've given you an upvote to do what I can to balance that. Expressing confusion over something like this is perfectly reasonable.

I am struggling to understand the advantages over the Lewis Carroll method, which I find very simple and quick. It seems to add quite a lot of complexity.

by reedf1 2y ago

I am struggling to understand the advantages over the Lewis Carroll method, which I find very simple and quick. It seems to add quite a lot of complexity.

jgrahamc 2y ago

Really? Colin's method seems pretty simple to memorize and work with. Especially since it's all addition mod 7. Given that the mod operator distributes over addition you can work answers out easily while working with small numbers. For example, what day of week was September 2, 1945? 45/4 = 11 (mod 7 = 4) 45 mod 7 = 3 (easy to work out from 7 times table) September = 6 2 So you've got 4 + 3 (disappears under mod 7) and 6 + 2 mod 7 = 1. So, the second world war ended on a Sunday.

ColinWright 2y ago

I'm struggling to see why you think this is more complex ... the methods seem completely equivalent to me. The Carroll method does: 1: A calculation for the Century-Item ... divide by 4, take overplus from 3, multiply remainder by 2. 2: A calculation for the Year-Item ... Add together the number of dozens, the overplus, and the number of 4’s in the overplus. 3: A calculation for the Month-Item ... alternatively, memorise a table: the required final numbers after division by 7 are January, 0; February, 3; March, 3; April, 6; May, 1; June, 4; July, 6; August 2; September, 5; October, 0; November, 3; and December, 5. Note that these numbers are exactly those in my table, minus 1. 4: Include the Day-Item. Then add them all (mod 7) and convert the number to a month. It's exactly equivalent to what I described, except the Carroll method has additional calculations for the year.

reedf1 2y ago
Possibly it was in the clarity of his explanation. That makes sense, thank you.

ColinWright 2y ago

I think it's unreasonable for you to have been downvoted, and I've given you an upvote to do what I can to balance that. Expressing confusion over something like this is perfectly reasonable.